Bottom Line:
Although APP is expressed in several tissues outside the human central nervous system, the functions of APP and its family members in other tissues are still poorly understood.We analyzed several topological properties of the APP interaction network and the biological and physiological properties of the proteins in the APP interaction network were also specified by gene ontologyand pathways analyses.Our approach allowed the identification of novel interactions and recognition of key APP interacting proteins for male reproduction, particularly in sperm-oocyte interaction.

Background: Amyloid precursor protein (APP) is widely recognized for playing a central role in Alzheimer's disease pathogenesis. Although APP is expressed in several tissues outside the human central nervous system, the functions of APP and its family members in other tissues are still poorly understood. APP is involved in several biological functions which might be potentially important for male fertility, such as cell adhesion, cell motility, signaling, and apoptosis. Furthermore, APP superfamily members are known to be associated with fertility. Knowledge on the protein networks of APP in human testis and spermatozoa will shed light on the function of APP in the male reproductive system.

Results: We performed a Yeast Two-Hybrid screen and a database search to study the interaction network of APP in human testis and sperm. To gain insights into the role of APP superfamily members in fertility, the study was extended to APP-like protein 2 (APLP2). We analyzed several topological properties of the APP interaction network and the biological and physiological properties of the proteins in the APP interaction network were also specified by gene ontologyand pathways analyses. We classified significant features related to the human male reproduction for the APP interacting proteins and identified modules of proteins with similar functional roles which may show cooperative behavior for male fertility.

Conclusions: The present work provides the first report on the APP interactome in human testis. Our approach allowed the identification of novel interactions and recognition of key APP interacting proteins for male reproduction, particularly in sperm-oocyte interaction.

Fig2: Diagram for the number of proteins interacting with APP from each dataset. The numbers indicate testis/sperm-annotated proteins interacting with APP from the different data sources; the numbers within parentheses represent the proteins enriched in testis and sperm. Self-connection for APP was neglected.

Mentions:
In order to identify APP interacting proteins expressed in human testis, an YTH screen of a human testis cDNA library was carried out using full-length human APP. The screen yielded 147 positive clones from a total of 3×108 clones screened. After partial or complete sequence analysis (depending on the length of the positive clone’s cDNAs), in silico searches of the GenBank DB allowed their identification and classification into three separate groups. Table 1 corresponds to library inserts encoding known proteins identified as putative APP interactors. The second and third groups correspond to clones putatively encoding novel APP interacting proteins with homology to genomic sequences and lists positives where the GenBank sequence similarity did not correspond to an annotated gene and false positive hits, respectively. Table 1 lists only 1 positive encoding a previously identified APP interacting protein (RANBP9) (Figure 1). 77 clones encoded 36 known proteins that were not previously associated with APP (Figure 1). Only the clones in Table 1 were included in the network and further functional analyses (Figure 2).Table 1

Fig2: Diagram for the number of proteins interacting with APP from each dataset. The numbers indicate testis/sperm-annotated proteins interacting with APP from the different data sources; the numbers within parentheses represent the proteins enriched in testis and sperm. Self-connection for APP was neglected.

Mentions:
In order to identify APP interacting proteins expressed in human testis, an YTH screen of a human testis cDNA library was carried out using full-length human APP. The screen yielded 147 positive clones from a total of 3×108 clones screened. After partial or complete sequence analysis (depending on the length of the positive clone’s cDNAs), in silico searches of the GenBank DB allowed their identification and classification into three separate groups. Table 1 corresponds to library inserts encoding known proteins identified as putative APP interactors. The second and third groups correspond to clones putatively encoding novel APP interacting proteins with homology to genomic sequences and lists positives where the GenBank sequence similarity did not correspond to an annotated gene and false positive hits, respectively. Table 1 lists only 1 positive encoding a previously identified APP interacting protein (RANBP9) (Figure 1). 77 clones encoded 36 known proteins that were not previously associated with APP (Figure 1). Only the clones in Table 1 were included in the network and further functional analyses (Figure 2).Table 1

Bottom Line:
Although APP is expressed in several tissues outside the human central nervous system, the functions of APP and its family members in other tissues are still poorly understood.We analyzed several topological properties of the APP interaction network and the biological and physiological properties of the proteins in the APP interaction network were also specified by gene ontologyand pathways analyses.Our approach allowed the identification of novel interactions and recognition of key APP interacting proteins for male reproduction, particularly in sperm-oocyte interaction.

Background: Amyloid precursor protein (APP) is widely recognized for playing a central role in Alzheimer's disease pathogenesis. Although APP is expressed in several tissues outside the human central nervous system, the functions of APP and its family members in other tissues are still poorly understood. APP is involved in several biological functions which might be potentially important for male fertility, such as cell adhesion, cell motility, signaling, and apoptosis. Furthermore, APP superfamily members are known to be associated with fertility. Knowledge on the protein networks of APP in human testis and spermatozoa will shed light on the function of APP in the male reproductive system.

Results: We performed a Yeast Two-Hybrid screen and a database search to study the interaction network of APP in human testis and sperm. To gain insights into the role of APP superfamily members in fertility, the study was extended to APP-like protein 2 (APLP2). We analyzed several topological properties of the APP interaction network and the biological and physiological properties of the proteins in the APP interaction network were also specified by gene ontologyand pathways analyses. We classified significant features related to the human male reproduction for the APP interacting proteins and identified modules of proteins with similar functional roles which may show cooperative behavior for male fertility.

Conclusions: The present work provides the first report on the APP interactome in human testis. Our approach allowed the identification of novel interactions and recognition of key APP interacting proteins for male reproduction, particularly in sperm-oocyte interaction.